Unlike spacecraft portrayed in science fiction stories,
Surveyor's laser was not designed to fend off hostile aliens
waiting in ambush. Instead, scientists will use the laser
altimeter, known as MOLA, to gather data that will enable them to
calculate the height of surface features.

This altitude determination process works by measuring the
time that a pulse of light takes to leave the spacecraft, reflect
off of the ground, and return to MOLA's collecting mirror. By
multiplying the reflection time by the speed of light, scientists
will be able to calculate Surveyor's altitude above the local
terrain to within 30 meters (98 feet) or better.

As the spacecraft flies above hills, valleys, craters, and
other surface features, its altitude above the ground will
constantly change. A combination of MOLA data with images from
the camera will allow scientists to construct a detailed
topographical atlas of the planet. Such maps will help in the
understanding of the geological forces that shaped Mars.